| Observation data Epoch J2000.0 Equinox J2000.0 |
|
|---|---|
| Constellation | Hercules |
| Right ascension | 17h 17m 40.48s[1] |
| Declination | +29° 13.6′ 38″ |
| Apparent magnitude (V) | +8.42 |
| Characteristics | |
| Spectral type | K2V |
| U−B color index | 0.27 |
| B−V color index | 0.73 |
| Variable type | none |
| Astrometry | |
| Radial velocity (Rv) | -9.427 km/s |
| Proper motion (μ) | RA: -72.75 mas/yr Dec.: -216.39 mas/yr |
| Parallax (π) | 41.58 ± 0.69[1] mas |
| Distance | 78 ± 1 ly (24.1 ± 0.4 pc) |
| Absolute magnitude (MV) | 4.12 |
| Other designations | |
HD 156668 is an orange dwarf star[2] found in the Hercules constellation which is approximately 78.4 light-years[3] away from the earth. The star has only about 27% of the Sun’s bolometric luminosity including a mass approximately 72% less and about 75% of its diameter. The star appears to have 85% enriched in iron in relation to the abundance of hydrogen as the Sun.[4][5][6]
From 1911 to 1915, Photographic Stellar Spectrum surveys[7] have been carried out by Annie Jump Cannon and Edward Charles Pickering. Anna Mary Palmer who was Henry Draper’s wife financed the study, it was also her husband who was responsible for the star’s designation in the Henry Draper Catalogue with subsequent extension (HD) although it was first designated as BD+29 2979[8] in the original catalogue that was published in 1863 by Friedrich Wilhelm Argelander due to its position and brightness of 324,198 stars between +90° and -2° declination in the span of an 11 year observation. A number of proper motion surveys was published in 1957 where 9,867 stars in the Southern hemisphere where high proper motion was detected.[9] The name BD was taken from a catalogue of the Bonner Durchmusterung (Bonn Survey)[10] where observations are abbreviated as BD. Latter study expansions were carried out by the Cape Photographic Durchmusterung observatory in Córdoba, Argentina and further extensions by Henry Lee Giclas who designated the star as G 181-34 in the Giclas catalogues. From 1990 to 1993, HD 156668 was observed at least twice and was featured at the 6th annual catalog of the Tokyo Photoelectric Meridian Circle (PMC) where it is one of 6649 stars observed.[11]
Andrew Howard announced the discovery of a Super-Earth in orbit around HD 156668. This planet is designated HD 156668 b. The announcement was made at the 215th American Astronomical Society meeting on January 4 to 7, 2010 in Washington D.C.. The planet orbits its star in only 4.6 days with a distance approximately 0.05 AU away from the parent star. The researchers used the wobble method where the resulting spectrum showed color shifts which was used to approximate the mass of the astronomical object. The observation revealed data that the exoplanet was at least 4.15 Earth masses.[12] Later observations revealed that the minimum mass is now 3.1 Earth masses.[13]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity |
|---|---|---|---|---|
| b | ≥3.1 ± 0.4 M⊕ | 0.0211 ± 0.0002 | 1.26984 ± 0.00007 | 0.000 |